1. Field of the Invention
The present invention relates to a method and apparatus for waterproofing a wire harness, such as one disposed in the boundary between an engine compartment and vehicle interior, where prevention of water penetration is necessary. Such waterproofing prevents water from penetrating into the gaps formed between the electrical wires of a wire harness. Such a wire harness is adapted to be fit into a grommet and passed through a hole formed in a panel of the vehicle.
2. Description of the Related Art
When a wire harness for a vehicle passes from the engine compartment to the passenger compartment, it is held in a grommet fitted around a hole in a vehicle panel separating the engine compartment from the passenger compartment. Such a configuration can prevent water seepage from the engine compartment into the passenger compartment.
The grommet conventionally has a tubular portion which extends to a funnel-shaped portion having an enlarged circular end section. The external face of the enlarged end section is provided with a circular groove that can engage with the peripheral rim of a hole formed in a vehicle panel. In this manner, the grommet and the panel hole provide an efficient seal against water seepage. In addition, the section of the wire harness that passes through the tubular portion is preferably gripped therein. Moreover, when a grommet is used in a water-filled area, the tubular portion is usually treated with a water-sealing agent.
For instance, JP-A-HEI 10-135657 discloses a process for treating electrical wires forming part of a wire harness, in which the wires are grouped in parallel, and the portion subject to water-protection treatment is covered with a water-sealing agent that has a viscosity of 1,000 to 2,000 poises. The electrical wires are then assembled to form a substantially round cross-section and passed through a grommet.
However, when the water-sealing agent has such a high level of viscosity, it must be pushed through forcibly between the electrical wires in order to form the waterproof portion properly. As a consequence, the process normally lowers work efficiency.
To improve the operation process, the viscosity of water-sealing agent may be lowered to less than 1,000 poises. However, such an agent creates a new problem, in that the agent tends to sag from the electrical wires.
Further, the wire harness protected in such a manner must be handled or controlled frequently, so as to check whether there is still no water infiltration. Such an operation further lowers the productivity.